1. Field of the Invention
This invention relates to an improved joint portion of a heat exchanger which is mounted on the heat exchanger, such as a condenser used in an air conditioner of an automobile, and is fixedly secured to an outer surface of a peripheral wall of a header which passes therethrough a fluid (e.g. a cooling medium) to be subjected to heat exchange.
2. Description of the Related Art
One known heat exchanger, used in an automobile air conditioner, is shown in FIG. 9. This heat exchanger 1 is constituted by combining various parts of an aluminum alloy together. More specifically, this heat exchanger 1, made of aluminum, comprises a plurality of parallel, spaced tubes 2 of a generally flattened cross-section, corrugated fins 3 each held between the corresponding two adjacent tubes 2 and 2, and a pair of headers 4 and 5 to which opposite ends of each of the tubes 2 are brazed liquid-tight, respectively, so that the two headers 4 and 5 are in communication with each other. A joint portion 6 is secured by brazing to an upper end portion of the header 4, and a joint portion 7 is secured by brazing to a lower end portion of the header 5, and for example, a piping joint 21 (see FIG. 12), which passes therethrough a fluid to be subjected to heat exchange, is adapted to be connected to the joint portion 6, 7. In FIG. 9, reference numeral 8 denotes a bracket by which the heat exchanger 1 is fixedly secured to a vehicle body. The brazing of a core portion 9 (comprising the tubes 2, the fins 3 and so on), and the brazing of the joint portions 6 and 7, are effected simultaneously by a known heat treatment in a furnace.
In the heat exchanger 1 of the above construction, the joint portion 6 serves as an inlet portion for the fluid (e.g. cooling medium) to be subjected to heat exchange whereas the joint portion 7 serves as an outlet portion for this fluid. With respect to the construction of the joint portions 6 and 7, for example, the joint portion 7 will be described briefly. A first through hole 11 is formed through a peripheral wall 10 of the header 5 at the lower end portion thereof. The joint portion 7 comprises a connector block 13 of a generally rectangular parallelepiped shape. An inner surface (left surface in FIGS. 10 and 11) of the connector block 13 is defined by a concavely-curved, arcuate surface 12 substantially equal in radius of curvature to the outer peripheral surface of the peripheral wall 10 of the header 5. The connector block 13 is fixedly secured to the header 5, with the concavely-curved surface 12 mated with the outer peripheral surface of the header 5, in such a manner that the first through hole 11 is covered with the connector block 13. A flow hole 14 is formed through a lower end portion of the connector block 13, and extends between the inner surface and the outer surface (right surface in FIGS. 10 and 11) thereof. The flow hole 14 has a smaller-diameter portion 16 open to the inner surface of the connector block 13, and a tapered hole portion 17 open to the outer surface of the connector block 13. A pipe piece 19 is fixedly fitted in the smaller-diameter portion 16 to form a first tubular portion 20 projecting from the concavely-curved surface 12. The first tubular portion 20 has such an outer diameter that it can be snugly fitted in the first through hole 11. A threaded hole 15 is formed through an upper end portion of the connector block 13, disposed above the flow hole 14, and extends between the inner and outer surfaces of the connector block 13 in parallel relation to the flow hole 14.
The connector block 13 is connected to the head 5, with the first tubular portion 20 fixedly fitted in the first through hole 11, and with the concavely-curved surface 12 mated with part of the outer peripheral surface of the header 5, and in this condition the connector block 13 is brazed to the header 5. As a result, the connector block 13 is fixedly secured liquid-tight to the header 5 in a manner shown in FIG. 10, thus forming the joint portion 7.
The piping joint 21 is connected to the joint portion 7 to form a flow passage for the fluid (e.g. cooling medium) to be subjected to heat exchange. For example, the piping joint 21 has a generally rectangular parallelepiped shape as shown in FIG. 12, and has an inner surface (left surface in FIG. 12) to be mated with the outer surface of the connector block 13. The piping joint 21 has at its lower end portion a cylindrical connection portion 22 which is adapted to be fitted in the flow hole 14. An O-ring 23 is mounted on an outer peripheral surface of the connection portion 22 intermediate opposite ends thereof. The connection portion 22 communicates with a pipe 24. A bolt insertion hole 25 is formed through an upper end portion of the piping joint 21 disposed above the pipe 24.
The piping joint 21 of this construction is connected to the joint portion 7, with the connection portion 22 fitted in the flow hole 14 in the joint portion 7 (FIGS. 10 and 11) and with the inner surface of the piping joint 21 mated with the outer surface of the connector block 13. In this condition, the O-ring 23 is held in intimate contact with the inner peripheral surface of the smaller-diameter portion 16, thus forming a seal therebetween. Then, a bolt 26 is inserted into the bolt insertion hole 25, and is threaded into the threaded hole 15 in the joint portion 7, and is tightened, thereby fixedly securing the piping joint 21 to the joint portion 7.
The joint portion 7 (The joint portion 6 has a similar construction, but is inverted in an upward-downward direction relative to the joint portion 7) and the piping joint 21 (A piping joint to be connected to the joint portion 6 has a similar construction) are constructed as described above, and are mounted on the heat exchanger 1. When the heat exchanger 1 is used as a condenser, the fluid (e.g. cooling medium) to be subjected to heat exchanger is fed into the header 4 via piping (not shown) connected to the joint portion 6. The thus fed fluid flows through the headers 4 and 5 and the tubes 2 in a sequentially manner, and further flows into the pipe 24 via the joint portion 7 and the piping joint 21.
However, in the joint portion of the conventional heat exchanger of the above construction, the thickness of the connector block 13 must be increased to a certain degree because of the formation of the threaded hole 15. Therefore, when the joint portion 7 is connected to the header 5, the amount t.sub.1 (FIG. 10) of projecting of the joint portion 7 from the header 5 is large, and the mounting operation can not be effected efficiently within a narrow engine room.
There has been another problem in the conventional joint portion. FIGS. 13 and 14 show another example of the conventional joint portion 7. The joint portion 7 comprises a connector body 47 fixedly secured to the outer surface of the upper end portion of the header 5, and a connection tube 48 provided on the connector body 47, and an end of a pipe (not shown), through which a cooling medium flows, is connected to the connection tube 48.
The connector body 47 has a flow hole 14, and an outer half (right half in FIGS. 13 and 14) of a pipe piece 19 is fitted in an inner half (left half in FIGS. 13 and 14) of the flow hole 14. That portion (larger-diameter portion 49) of the flow hole 14 close to the concavely-curved surface 12 is larger in diameter than that portion thereof close to the outer surface. The outer half of the pipe piece 19 is fitted in the larger-diameter portion 49. The inner half of the pipe piece 19 is fitted in a through hole 11 formed in the header 5, and communicates with the bore of the header 5. In FIGS. 13 and 14, reference numeral 15 denotes a threaded hole used for threadedly fixing a mounting block of a liquid tank or other device. A peripheral groove 50 is formed in an outer peripheral surface of the connection tube 48 formed integrally with the connector body 47, and an O-ring is mounted in this peripheral groove 50 so as to form a seal between the connection tube 48 and the pipe connected to this connection tube 48.
The joint portion 7 of the above construction for the heat exchanger is formed by skiving or cutting a single block of an aluminum alloy in such a manner that the connecting tube 48 is integral with the connector body 47. More specifically, as shown in FIG. 15, the block 51, having the concavely-curved surface 12 substantially conforming to the outer surface of the headers 4 and 5 (FIGS. 9 and 13), is cut from the outer side, thereby removing those portions indicated by dots-and-dash lines, thus forming a projected portion 52 serving as the connection tube 48. Then, the flow hole 14 is formed through the block 51 axially of the projected portion 52. As described above, that portion of the flow hole 14 close to the concavely-curved surface 12 defines the larger-diameter portion 49 into which the pipe piece 19 is fitted. Thus, the cutting operation and the formation of the flow hole 14 are troublesome, and the efficiency of processing the material, as well as the yield of the material, is poor, which leads to a high cost.